1. Field of the Invention
This invention relates to digital laser projection systems.
2. Description of Related Art
Conventional cinemas utilize film projection systems that illuminate film with a high-brightness source of white light. A moving image in film is represented in a series of frames that are rapidly drawn over an aperture in the projector, and the resulting image is projected onto a screen using projection optical systems. When viewed, the projected image appears to be a video xe2x80x9cmoving picturexe2x80x9d. Although in wide use, such projection systems have a number of problems; for example, film wears down over time, brightness is inherently limited, and the individual film copies can be expensive.
While traditional cinemas have relied almost exclusively upon film projectors, cinemas of the future will utilize an alternative projection system in which red, green, and blue light is modulated by light modulators and then projected onto a screen using projection optics. One such proposed alternative projection system utilizes a red laser, a green laser, and a blue laser, each of which are individually modulated in a series of xe2x80x9cframesxe2x80x9d and then projected onto a screen to create a full color image. One disadvantage of such a system is that the red, green, and blue lasers must be individually synchronized with their light modulators, which requires additional hardware. Another disadvantage is that the color combiner that combines the modulated red, green, and blue beams is difficult and expensive to implement in such a way that the three colors are precisely registered on top of each other and thereby appear as a single image. Even a slight misregistration of any one of the three colors can cause serious problems with the image.
Full-color digital movie data typically has a red green and blue (RGB) format in which red, green, and blue data has a respective brightness value stored for each pixel and each frame. Theoretically, this RGB data can be straightforwardly projected by a digital projection system by modulating red, green, and blue laser beams, if such a system were available. One advantage of a laser projection system is that digital movies can be distributed entirely in a digital format such as a computer file. A digital image format provides improved image quality and consistency over time because, unlike film, digital images do not xe2x80x9cwear downxe2x80x9d. Furthermore, a digital movie format can be more easily combined with other information such as supplemental commercials or directed advertising. Generally, digital movie formats are a much more cost-effective and efficient way of distribution than film, and it would be useful to provide a cost-effective projection system so that digital movie formats could be used in place of film.
A multi-screen laser projection system for projecting images onto a plurality of screens is disclosed comprising a laser source that generates a plurality of laser beams, at least two of the laser beams having differing color, an image display control system that receives image data indicative of the images to be projected, a plurality of modulator arms, each modulator arm including a light modulator coupled to the image control system, and an optical switch situated between the laser source and the plurality of modulator arms, the optical switch coupled to the image display control system and arranged to receive the plurality of beams from the laser source and switch each of the beams to a selected one of the modulator arms.
A multi-screen projection system is disclosed herein that utilizes a shared laser source switched among several different modulator arms in order to illuminate each modulator with a sequence of colors during each frame. During the course of a frame, each of the colors becomes incident upon the modulator. Each screen displays an image that is generated by modulating the individual pixels in its respective two-dimensional light modulator array. Specifically, during the period while a color is illuminating the light modulator, each individual pixel is modulated to provide the illumination corresponding to that color for that pixel for that frame. Proper registration of all colors on each pixel is facilitated because a single modulator is used to modulate all colors for each screen.
The projection system disclosed herein can provide a cost-effective, true digital projection display system, which allows movies to be transferred in an electronic digital format, providing consistency in color rendering and image quality over time without the degradation experienced by film. Furthermore, the projection system can make more efficient use of laser energy than conventional systems. In some embodiments, only a single source of laser energy for each color is required to illuminate multiple screens, thereby simplifying the projection system and reducing cost.
Advantageously, the projection display system disclosed herein can be implemented with high brightness and/or high resolution displays. As compared with a laser scanning system, beam requirements for the disclosed system can be less stringent, which allows lower cost optical systems to be used and permits higher power. For example, a diffraction limited beam is not required in some embodiments, thereby simplifying the optics and allowing use of larger fibers, among other advantages.
In one example herein, the two-dimensional light modulator array comprises a digital micromirror device (DMD), although other embodiments could utilize another type of light modulator. A DMD is a two-dimensional light modulator that modulates the incident light by moving each individual micromirror between a first and second state. In the first state of the pixel, the light incident upon the micromirror is projected toward the projection system for display, and in the second state, the incident light is directed elsewhere, such as to a beam dump or otherwise.